A man describes a lifelong pattern of emotional coolness and detachment from others, with little genuine wish for close relationships, taking real enjoyment instead from solitary intellectual pursuits, and appearing entirely content with this way of life rather than distressed by it. What is this?

This is schizoid personality disorder: pervasive emotional coolness and detachment, little genuine wish for close relationships, and real, undistressed enjoyment of solitary pursuits, exactly as described. It is not depersonalisation, which differs from this pattern in quality — depersonalisation is described by the person as distressing, with a subjective sense of being cut off or outside oneself, whereas this detachment carries no such distress. It is not anxious (avoidant) personality disorder, in which the person has a strong underlying wish for relationships but is held back by shyness and poor social skills. And it is not schizotypal personality disorder, which retains some fluctuating capacity for relationships rather than a uniform, stable detachment.